A school bus carrying students from Regional School Unit 18 was evacuated Friday on Mary Lane in Oakland after heating unit malfunctioned and overheated.

The Oakland Fire Department was called to the bus shortly after 7 a.m. According to David Boag, a firefighter with the department, occupants smelled something burning. The bus was evacuated and students were transferred to another bus by the time fire crews arrived, Boag said.

Lennie Goff, RSU 18 transportation director, said the cause of the evacuation was a fan motor that had burned out, a fairly common malfunction. There was no fire, but students and the driver smelled something hot, Goff said.

“The driver erred on the side of safety and we called the Fire Department,” Goff said.

“Anytime we smell what seems to be wires that are hot or anything like that, we evacuate the bus,” Goff added. “We’re not going to take a chance.”

Students were calm and the evacuation went off without a hitch, Goff added. A second bus was on the scene within five minutes to pick up the students, he said.

Goff said he didn’t know the ages of the children on the bus at the time of the incident, but it carries students in kindergarten through grade 12 and was at the beginning of its route.

Fan motors on the buses commonly wear out and break. Goff said the department loses 15 to 20 of the motors a year. With each bus equipped with six fan motors, there are about 250 of the units in the RSU 18 fleet, Goff said. The bus with the broken motor would be fixed and put back on the road Friday afternoon, he added.